diff --git a/CMakeLists.txt b/CMakeLists.txt
index 26ae4685b62..61c49f32c2f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -103,6 +103,7 @@ zephyr_compile_options(
   -ffreestanding
   -Wno-main
   ${NOSTDINC_F}
+  ${TOOLCHAIN_C_FLAGS}
 )
 
 zephyr_compile_options(
@@ -230,6 +231,7 @@ else() # GCC assumed
     -Wno-unused-but-set-variable
     -fno-reorder-functions
     )
+
   if(NOT ${ZEPHYR_TOOLCHAIN_VARIANT} STREQUAL "xcc")
     zephyr_cc_option(-fno-defer-pop)
   endif()
@@ -637,6 +639,14 @@ set(zephyr_lnk
   )
 
 if(CONFIG_GEN_ISR_TABLES)
+  if(CONFIG_GEN_SW_ISR_TABLE)
+    list(APPEND GEN_ISR_TABLE_EXTRA_ARG --sw-isr-table)
+  endif()
+
+  if(CONFIG_GEN_IRQ_VECTOR_TABLE)
+    list(APPEND GEN_ISR_TABLE_EXTRA_ARG --vector-table)
+  endif()
+
   # isr_tables.c is generated from zephyr_prebuilt by
   # gen_isr_tables.py
   add_custom_command(
@@ -653,8 +663,7 @@ if(CONFIG_GEN_ISR_TABLES)
     --kernel $<TARGET_FILE:zephyr_prebuilt>
     --intlist isrList.bin
     $<$<BOOL:${CMAKE_VERBOSE_MAKEFILE}>:--debug>
-    --sw-isr-table
-    --vector-table
+    ${GEN_ISR_TABLE_EXTRA_ARG}
     DEPENDS zephyr_prebuilt
     )
   set_property(GLOBAL APPEND PROPERTY GENERATED_KERNEL_SOURCE_FILES isr_tables.c)
diff --git a/arch/arm/CMakeLists.txt b/arch/arm/CMakeLists.txt
index f96bbaa7662..ed20e40320c 100644
--- a/arch/arm/CMakeLists.txt
+++ b/arch/arm/CMakeLists.txt
@@ -15,7 +15,6 @@ endif()
 
 zephyr_compile_options(
   -mabi=aapcs
-  ${TOOLCHAIN_C_FLAGS}
   ${ARCH_FLAG}
   )
 
diff --git a/arch/posix/CMakeLists.txt b/arch/posix/CMakeLists.txt
index ca278103505..2d708beadec 100644
--- a/arch/posix/CMakeLists.txt
+++ b/arch/posix/CMakeLists.txt
@@ -8,7 +8,6 @@ zephyr_compile_options(
   -m32
   -MMD
   -MP
-  ${TOOLCHAIN_C_FLAGS}
   ${ARCH_FLAG}
   -include ${PROJECT_SOURCE_DIR}/arch/posix/include/posix_cheats.h
   )
diff --git a/cmake/compiler/gcc.cmake b/cmake/compiler/gcc.cmake
index db03eca893e..044c0498eef 100644
--- a/cmake/compiler/gcc.cmake
+++ b/cmake/compiler/gcc.cmake
@@ -1,10 +1,13 @@
+set_ifndef(CC gcc)
+set_ifndef(C++ g++)
+
 # Configures CMake for using GCC, this script is re-used by several
 # GCC-based toolchains
-
-find_program(CMAKE_C_COMPILER ${CROSS_COMPILE}gcc     PATH ${TOOLCHAIN_HOME} NO_DEFAULT_PATH)
+find_program(CMAKE_C_COMPILER ${CROSS_COMPILE}${CC}   PATH ${TOOLCHAIN_HOME} NO_DEFAULT_PATH)
 find_program(CMAKE_OBJCOPY    ${CROSS_COMPILE}objcopy PATH ${TOOLCHAIN_HOME} NO_DEFAULT_PATH)
 find_program(CMAKE_OBJDUMP    ${CROSS_COMPILE}objdump PATH ${TOOLCHAIN_HOME} NO_DEFAULT_PATH)
-#find_program(CMAKE_LINKER     ${CROSS_COMPILE}ld      PATH ${TOOLCHAIN_HOME} NO_DEFAULT_PATH)
+find_program(CMAKE_AS         ${CROSS_COMPILE}as      PATH ${TOOLCHAIN_HOME} NO_DEFAULT_PATH)
+find_program(CMAKE_LINKER     ${CROSS_COMPILE}ld      PATH ${TOOLCHAIN_HOME} NO_DEFAULT_PATH)
 find_program(CMAKE_AR         ${CROSS_COMPILE}ar      PATH ${TOOLCHAIN_HOME} NO_DEFAULT_PATH)
 find_program(CMAKE_RANLIB     ${CROSS_COMPILE}ranlib  PATH ${TOOLCHAIN_HOME} NO_DEFAULT_PATH)
 find_program(CMAKE_READELF    ${CROSS_COMPILE}readelf PATH ${TOOLCHAIN_HOME} NO_DEFAULT_PATH)
@@ -22,10 +25,10 @@ TOOLCHAIN_HOME: ${TOOLCHAIN_HOME}
 endif()
 
 if(CONFIG_CPLUSPLUS)
-  set(cplusplus_compiler ${CROSS_COMPILE}g++)
+  set(cplusplus_compiler ${CROSS_COMPILE}${C++})
 else()
-  if(EXISTS ${CROSS_COMPILE}g++)
-    set(cplusplus_compiler ${CROSS_COMPILE}g++)
+  if(EXISTS ${CROSS_COMPILE}${C++})
+    set(cplusplus_compiler ${CROSS_COMPILE}${C++})
   else()
     # When the toolchain doesn't support C++, and we aren't building
     # with C++ support just set it to something so CMake doesn't
@@ -58,56 +61,64 @@ foreach(file_name include include-fixed)
   list(APPEND NOSTDINC ${_OUTPUT})
 endforeach()
 
-include(${ZEPHYR_BASE}/cmake/gcc-m-cpu.cmake)
+if("${ZEPHYR_TOOLCHAIN_VARIANT}" STREQUAL "xcc")
 
-if("${ARCH}" STREQUAL "arm")
-  list(APPEND TOOLCHAIN_C_FLAGS
-    -mthumb
-    -mcpu=${GCC_M_CPU}
-    )
+  LIST(APPEND TOOLCHAIN_LIBS gcc)
+  LIST(APPEND TOOLCHAIN_LIBS hal)
 
-  include(${ZEPHYR_BASE}/cmake/fpu-for-gcc-m-cpu.cmake)
+else()
+  include(${ZEPHYR_BASE}/cmake/gcc-m-cpu.cmake)
 
-  if(CONFIG_FLOAT)
-    list(APPEND TOOLCHAIN_C_FLAGS -mfpu=${FPU_FOR_${GCC_M_CPU}})
-    if    (CONFIG_FP_SOFTABI)
-      list(APPEND TOOLCHAIN_C_FLAGS -mfloat-abi=softfp)
-    elseif(CONFIG_FP_HARDABI)
-      list(APPEND TOOLCHAIN_C_FLAGS -mfloat-abi=hard)
+  if("${ARCH}" STREQUAL "arm")
+    list(APPEND TOOLCHAIN_C_FLAGS
+      -mthumb
+      -mcpu=${GCC_M_CPU}
+      )
+
+    include(${ZEPHYR_BASE}/cmake/fpu-for-gcc-m-cpu.cmake)
+
+    if(CONFIG_FLOAT)
+      list(APPEND TOOLCHAIN_C_FLAGS -mfpu=${FPU_FOR_${GCC_M_CPU}})
+      if    (CONFIG_FP_SOFTABI)
+        list(APPEND TOOLCHAIN_C_FLAGS -mfloat-abi=soft)
+      elseif(CONFIG_FP_HARDABI)
+        list(APPEND TOOLCHAIN_C_FLAGS -mfloat-abi=hard)
+      endif()
     endif()
+  elseif("${ARCH}" STREQUAL "arc")
+    list(APPEND TOOLCHAIN_C_FLAGS
+      -mcpu=${GCC_M_CPU}
+      )
   endif()
-elseif("${ARCH}" STREQUAL "arc")
-  list(APPEND TOOLCHAIN_C_FLAGS
-	  -mcpu=${GCC_M_CPU}
+
+  execute_process(
+    COMMAND ${CMAKE_C_COMPILER} ${TOOLCHAIN_C_FLAGS} --print-libgcc-file-name
+    OUTPUT_VARIABLE LIBGCC_FILE_NAME
+    OUTPUT_STRIP_TRAILING_WHITESPACE
     )
-endif()
 
-execute_process(
-  COMMAND ${CMAKE_C_COMPILER} ${TOOLCHAIN_C_FLAGS} --print-libgcc-file-name
-  OUTPUT_VARIABLE LIBGCC_FILE_NAME
-  OUTPUT_STRIP_TRAILING_WHITESPACE
-  )
+  assert_exists(LIBGCC_FILE_NAME)
 
-execute_process(
-  COMMAND ${CMAKE_C_COMPILER} ${TOOLCHAIN_C_FLAGS} --print-multi-directory
-  OUTPUT_VARIABLE NEWLIB_DIR
-  OUTPUT_STRIP_TRAILING_WHITESPACE
-  )
+  get_filename_component(LIBGCC_DIR ${LIBGCC_FILE_NAME} DIRECTORY)
 
-assert_exists(LIBGCC_FILE_NAME)
+  assert_exists(LIBGCC_DIR)
 
-get_filename_component(LIBGCC_DIR ${LIBGCC_FILE_NAME} DIRECTORY)
+  LIST(APPEND LIB_INCLUDE_DIR "-L\"${LIBGCC_DIR}\"")
+  LIST(APPEND TOOLCHAIN_LIBS gcc)
 
-assert_exists(LIBGCC_DIR)
+  if(SYSROOT_DIR)
+    # The toolchain has specified a sysroot dir that we can use to set
+    # the libc path's
+    execute_process(
+      COMMAND ${CMAKE_C_COMPILER} ${TOOLCHAIN_C_FLAGS} --print-multi-directory
+      OUTPUT_VARIABLE NEWLIB_DIR
+      OUTPUT_STRIP_TRAILING_WHITESPACE
+      )
 
-LIST(APPEND LIB_INCLUDE_DIR "-L\"${LIBGCC_DIR}\"")
-LIST(APPEND TOOLCHAIN_LIBS gcc)
+    set(LIBC_LIBRARY_DIR "\"${SYSROOT_DIR}\"/lib/${NEWLIB_DIR}")
+    set(LIBC_INCLUDE_DIR ${SYSROOT_DIR}/include)
+  endif()
 
-if(SYSROOT_DIR)
-  # The toolchain has specified a sysroot dir that we can use to set
-  # the libc path's
-  set(LIBC_INCLUDE_DIR ${SYSROOT_DIR}/include)
-  set(LIBC_LIBRARY_DIR "\"${SYSROOT_DIR}\"/lib/${NEWLIB_DIR}")
 endif()
 
 # For CMake to be able to test if a compiler flag is supported by the
diff --git a/cmake/toolchain/xcc.cmake b/cmake/toolchain/xcc.cmake
new file mode 100644
index 00000000000..56caa3fe261
--- /dev/null
+++ b/cmake/toolchain/xcc.cmake
@@ -0,0 +1,18 @@
+set(TOOLCHAIN_HOME /opt/xtensa/XtDevTools/install/tools/$ENV{TOOLCHAIN_VER}/XtensaTools)
+
+set(COMPILER gcc)
+
+set(CROSS_COMPILE_TARGET xt)
+set(SYSROOT_TARGET       xtensa-elf)
+
+set(CROSS_COMPILE  ${TOOLCHAIN_HOME}/bin/${CROSS_COMPILE_TARGET}-)
+set(SYSROOT_DIR    ${TOOLCHAIN_HOME}/${SYSROOT_TARGET})
+set(XCC_BUILD      $ENV{XTENSA_BUILD_PATHS}/$ENV{TOOLCHAIN_VER}/${CONFIG_SOC})
+
+# xt-xcc does not support -Og, so make it -O0
+set(OPTIMIZE_FOR_DEBUG_FLAG "-O0")
+
+set(CC xcc)
+set(C++ xc++)
+
+list(APPEND TOOLCHAIN_C_FLAGS -fms-extensions)
diff --git a/include/toolchain/xcc.h b/include/toolchain/xcc.h
index 4ce2d3bdffb..902d658892c 100644
--- a/include/toolchain/xcc.h
+++ b/include/toolchain/xcc.h
@@ -36,4 +36,12 @@
 
 #endif /* __GCC_LINKER_CMD__ */
 
+#define __builtin_unreachable() __ASSERT(0, "Unreachable code")
+
+/* TODO: XCC doesn't define the below macros which are useful for checking
+ * overflows. This needs to be fixed.
+ */
+#define __builtin_add_overflow(a, b, output)	({ *output = (a) + (b); 0; })
+#define __builtin_mul_overflow(a, b, output)	({ *output = (a) * (b); 0; })
+
 #endif